Cerebrotendinous xanthomatosis is a recessively inherited in born of bile acid synthesis due to a mutation in sterol 27-hydroxylase (CYP27A1). Patients with this disease suffer from xanthomas located in the brain and tendon, accelerated atherosclerosis progression neurologic disease and cataracts. Plasma cholesterol levels are normal but cholestanol and C-27 bile alcohol that precursor of bile acid synthesis accumulate and are believe are responsible for the atherosclerosis, xanthomas and neurologic disease. Analysis of the bile reveal a severe sufficiency of the primary bile acid chenodeoxycholic acid that can not be produce because of the inherited defect. However, replacement of chenodeoxycholic acid in the enterohepatic pool inhibit abnormal bile acid synthesis and reduces the elevated level of cholestanol and C-27 bile alcohol this therapy halt the neurologic disease and prevents symptomatic atherosclerosis developing.